The present invention relates to the field of electronic devices. The invention is illustrated in an example with regard to a hard disk cleaning technique, including a method and apparatus, but it will be recognized that the invention has a wider range of applicability. Merely by way of example, the invention can also be applied to the manufacture of raw wafers, lead frames, medical devices, flat panel displays, microelectronic masks, integrated circuits, and other applications requiring high purity wet processing such as steps of rinsing, cleaning, drying, and the like.
Industry utilizes or has proposed various techniques to rinse and dry hard disks. An example of a conventional technique used to rinse a hard disk is a cascade rinse. The cascade rinse utilizes a cascade rinser, which includes inner and outer chambers, each separated by a partition. Rinse water flows from a water source into the inner chamber. The rinse water from the inner chamber cascades into the outer chamber. An in-process disk is typically rinsed in the cascade rinser by dipping the disk into the rinse water of the inner chamber. This process is often used to neutralize and remove residual material from the disk.
A limitation with the cascade rinser is that "dirty water" often exists in the first chamber. The dirty water typically includes residual material as well as "particles" which often attach to the hard disk. These particles can cause defects in the disk. Another limitation with the cascade rinser is hard disks from the cascade rinser must still undergo a drying operation. Accordingly, the cascade rinse often cannot clean or remove particles from the hard disk.
Another technique often used to rinse hard disks is the "quick dump" method. The quick dump method relies upon the rapid deployment of water from the rinse tank to remove water and impurities from the disk. A limitation with this method is its inability to actually clean or remove particles from the disk. In fact, the rapid deployment of water from the tank often transfers more particles onto the disk. In addition, disks from the quick dump tank must still undergo a drying operation, further increasing the number of particles on the disks and processing complexity.
A further technique used to both rinse and dry disks relies upon a spin rinse/dryer. The spin rinse/dryer uses a combination of rinse water spray to rinse, and centrifugal force to remove water from the disk. The drying step often removes the water from the disk substantially by centrifugal force and evaporation. However, the spin rinse/dryer often introduces more particles onto the disk. In fact, initially dissolved or suspended contaminants such as particles in the water are often left on the disk, thereby reducing the number of "good" disks. Another limitation with the spin rinse/dryer is its complex mechanical design with moving parts and the like. The complex mechanical design often leads to certain problems such as greater downtime, disk breakage, more spare parts, greater costs, among others. A further limitation is static electricity often builds up on the disks during the spin cycle, thereby attracting even more particles onto the surface of the disk. Accordingly, the spin rinse/drying does not clean or remove particles from the hard disk.
Other techniques used to dry hard disks include an isopropyl alcohol (IPA) vapor dryer, full displacement IPA dryer, and others. These IPA-type dryers often rely upon a large quantity of a solvent such as isopropyl alcohol and other volatile organic liquids to facilitate drying of the hard disk. An example of such a technique is described in U.S. Pat. No. 4,911,761, and its related applications, in the name of McConnell et al. and assigned to CFM Technologies, Inc. McConnell et al. generally describes the use of a super-heated or saturated drying vapor as a drying fluid. This super-heated or saturated drying vapor often requires the use of large quantities of a hot volatile organic material. The super-heated or saturated drying vapor forms a thick organic vapor layer overlying the rinse water to displace (e.g., plug flow) such rinse water with the drying vapor. The thick organic vapor layer forms an azeotropic mixture with water, which will condense on hard disk surfaces, and will then evaporate to dry the disk.
A limitation with this type of dryer is its use of the large solvent quantity, which is hot, highly flammable, and extremely hazardous to health and the environment. Another limitation with such a dryer is its cost, which is often quite expensive. In fact, this dryer needs a vaporizer and condenser to handle the large quantities of hot volatile organic material. Still further, it has been determined that large quantities of hot volatile organic material are typically incompatible with certain disks.
Still another technique relies upon a hot deionized ("DI") process water to rinse and promote drying of the hard disk. By way of the hot DI water, the liquid on the disk evaporates faster and more efficiently than standard room temperature DI water. However, hot water often produces stains on the disk, and also promotes buildup of bacterial and other particles. Hot water can also damage the disk, thereby reducing the number of good disks produced. Another limitation is hot water is often expensive to heat, and hot DI water is also an aggressive solvent. As an aggressive solvent, it often deteriorates equipment and facilities, thereby increasing maintenance operation costs.
It is clearly desirable to have a cleaning technique, including a method and apparatus, that actually removes particles, prevents additional particles, and does not introduce stains on the hard disks. The cleaning technique should also dry the disks, without other adverse results. A further desirable characteristic includes reducing or possibly eliminating the residual water left on disk surfaces and edges when water is removed (a meniscus). The water left on such surfaces and edges often attracts and introduces more particles onto the disk.
From the above, it is seen that a cleaning method and apparatus for hard disks that is safe, easy, and reliable is often desired.